linux-kernel - Re: [PATCH V4 1/9] PM / OPP: Allow OPP table to be used for power-domains

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Date:   Wed, 26 Apr 2017 14:55:32 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Rajendra Nayak <rnayak@...eaurora.org>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Rafael Wysocki <rjw@...ysocki.net>, ulf.hansson@...aro.org,
        Kevin Hilman <khilman@...aro.org>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        robh+dt@...nel.org, lina.iyer@...aro.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH V4 1/9] PM / OPP: Allow OPP table to be used for
 power-domains

On Wed, Apr 26, 2017 at 10:02:39AM +0530, Rajendra Nayak wrote:
> > On 17/04/17 06:27, Viresh Kumar wrote:

> >>> If we are looking this power-domains with performance as just some
> >>> *advanced regulators*, I don't like the complexity added.

> + Mark

> I don;t see any public discussions on why we ruled out using regulators to
> support this but maybe there were some offline discussions on this.

> Mark, this is a long thread, so just summarizing here to give you the context.

> At qualcomm, we have an external M3 core (running its own firmware) which controls
> a few voltage rails (including AVS on those). The devices vote for the voltage levels
> (or performance levels) they need by passing an integer value to the M3 (not actual
> voltage values). Since that didn't fit well with the existing regulator apis it was

As I'm getting fed up of saying: if the values you are setting are not
voltages and do not behave like voltages then the hardware should not be
represented as a voltage regulator since if they are represented as
voltage regulators things will expect to be able to control them as
voltage regulators.  This hardware is quite clearly providing OPPs
directly, I would expect this to be handled in the OPP code somehow.

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